The present invention relate to a high power electrical contactor. More specifically, embodiments of the present invention relate to an electrical contactor having improved bridge contact terminals used to carry high current, such as power transformers, water pumps and the like, in heating and air conditioning applications.
Certain electrical applications, such as noted above, utilize electrical contactors having sets of contacts that are normally open (or separated). The contacts are closed (or joined) to supply power to a particular device. For example, an air conditioning unit includes a contactor which has terminals that are oppositely aligned from each other and electrically connected to separate cooling features of the unit. The contactor also includes an actuator holding a bridge contact proximate the terminals in an initial open position. The contactor is electrically connected to a thermostat that sends an electrical signal to the contactor upon reading a predetermined temperature. When the contactor receives the electrical signal, the contactor introduces a magnetic field about the actuator which drives the actuator to a final closed position. In the final closed position, the contact surfaces on the bridge contact engage contact surfaces on the terminals to power the cooling features within the air conditioning unit.
The bridge contact rests on a bridge seat of the actuator which is biased toward the initial open position by a spring. The bridge seat and activator are oriented parallel to the contact surfaces on the terminal, thereby similarly orienting the contact surfaces of the bridge contact parallel to the terminal contact surfaces. This parallel alignment ensures that, as the actuator moves the bridge contacts from the initial open position to the final closed position, the contact surfaces of the bridge contact simultaneously evenly engage the entire contact surfaces of the terminals. Similarly, during disengagement, as the actuator moves the bridge contact away from the contact surfaces of the terminals, the actuator maintains a parallel alignment between the bridge contact surfaces and the terminal contact surfaces. Hence, the contact surfaces of the terminals simultaneously evenly disengage the entire contact surfaces of the bridge contact. The contact surfaces of the bridge contact thus move linearly upward and downward during engagement and disengagement while remaining in the desired parallel alignment with the contact surfaces of the terminals.
However, conventional connectors of the type described above suffer from several drawbacks. In particular, an electrical arc is created between the contact surfaces of a terminal and the contact surface of the bridge contact during engagement. The electrical arc often creates a tack weld between the bridge contact surface and the terminal contact surfaces. The tack weld may be sufficiently strong to overcome the mechanical biasing force continuously induced by the spring. Hence, when the magnetic field closing the contacts is released, the spring is unable to break the tack weld. Hence, the tack weld may prevent the contact surfaces from disengaging from each other even though the spring returns the actuator to the initial open position. Thus, the cooling unit may continue to operate long after the temperature has been satisfactorily reduced. Also, the welded contact surface and contact tip may resist movement of the actuator to the initial open position such that the actuator, bridge contact, or terminals become displaced or damaged. Additionally, even if the contact surface and the contact tip are separated by the movement of the actuator after being welded to each other, the contact surface and contact tip may be damaged and in need of replacement. Therefore, the contact surface and contact tip may require constant monitoring and, when the contact tip and contact surface are welded to each other, the entire contactor needs to be replaced, which consumes time and money.
Therefore, a need exists for a contactor that overcomes the above problems and addresses other concerns experienced in the prior art.